/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.dex.code.form;

import java.util.BitSet;

import com.android.dx.dex.code.CstInsn;
import com.android.dx.dex.code.DalvInsn;
import com.android.dx.dex.code.InsnFormat;
import com.android.dx.rop.code.RegisterSpec;
import com.android.dx.rop.code.RegisterSpecList;
import com.android.dx.rop.cst.Constant;
import com.android.dx.rop.cst.CstFieldRef;
import com.android.dx.rop.cst.CstString;
import com.android.dx.rop.cst.CstType;
import com.android.dx.util.AnnotatedOutput;

/**
 * Instruction format {@code 31c}. See the instruction format spec for details.
 */
public final class Form31c extends InsnFormat {

	/** {@code non-null;} unique instance of this class */
	public static final InsnFormat THE_ONE = new Form31c();

	/**
	 * Constructs an instance. This class is not publicly instantiable. Use
	 * {@link #THE_ONE}.
	 */
	private Form31c() {
		// This space intentionally left blank.
	}

	/** {@inheritDoc} */
	@Override
	public String insnArgString(DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		return regs.get(0).regString() + ", " + cstString(insn);
	}

	/** {@inheritDoc} */
	@Override
	public String insnCommentString(DalvInsn insn, boolean noteIndices) {
		if (noteIndices) {
			return cstComment(insn);
		} else {
			return "";
		}
	}

	/** {@inheritDoc} */
	@Override
	public int codeSize() {
		return 3;
	}

	/** {@inheritDoc} */
	@Override
	public boolean isCompatible(DalvInsn insn) {
		if (!(insn instanceof CstInsn)) {
			return false;
		}

		RegisterSpecList regs = insn.getRegisters();
		RegisterSpec reg;

		switch (regs.size()) {
		case 1: {
			reg = regs.get(0);
			break;
		}
		case 2: {
			/*
			 * This format is allowed for ops that are effectively 2-arg but
			 * where the two args are identical.
			 */
			reg = regs.get(0);
			if (reg.getReg() != regs.get(1).getReg()) {
				return false;
			}
			break;
		}
		default: {
			return false;
		}
		}

		if (!unsignedFitsInByte(reg.getReg())) {
			return false;
		}

		CstInsn ci = (CstInsn) insn;
		Constant cst = ci.getConstant();

		return (cst instanceof CstType) || (cst instanceof CstFieldRef)
				|| (cst instanceof CstString);
	}

	/** {@inheritDoc} */
	@Override
	public BitSet compatibleRegs(DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		int sz = regs.size();
		BitSet bits = new BitSet(sz);
		boolean compat = unsignedFitsInByte(regs.get(0).getReg());

		if (sz == 1) {
			bits.set(0, compat);
		} else {
			if (regs.get(0).getReg() == regs.get(1).getReg()) {
				bits.set(0, compat);
				bits.set(1, compat);
			}
		}

		return bits;
	}

	/** {@inheritDoc} */
	@Override
	public void writeTo(AnnotatedOutput out, DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		int cpi = ((CstInsn) insn).getIndex();

		write(out, opcodeUnit(insn, regs.get(0).getReg()), cpi);
	}
}
